1. (Field of the Invention)
The present invention relates to a structure of a fireproof frame for building opening portions such as openings for windows, doors, etc.
2. (Description of the Prior Art)
A wood frame which has been used in the past as a frame for an opening portion has an appearance of beautiful wood grain and is excellent in fabricability and heat retaining property, but it has a fatal drawback of being burnt out or spreading fire upon fire accident. Therefore, it can not be used as a fireproof frame for buildings.
In view of the above, conventional structure of a fireproof frame for the opening portion employed usually comprises frames made of iron, aluminum or inorganic substance combined with heat insulating material or fireproof material, or further applied with surface decoration by appending thin wood veneer or applying printing or painting.
Although a fireproof frame made of metal is effective for preventing fire, it involves drawbacks that effective heat insulation is difficult due to heat or cold bridges present in connection portions and that a frame made of inorganic substance is poor in fabricability and can not firmly retain nails or screws for attaching auxiliary parts.